Bashar Assad may finally have gone too far. In the wake of the Syrian dictator’s suspected nerve-gas attack last week, escalating rhetoric from Washington, Europe and Israel suggests a growing consensus for a military strike in response. But given Barack Obama’s well-known aversion to becoming entangled in that country’s savage civil war, and a growing belief that a stalemate might best serve U.S. interests anyway, any attack on Syria is unlikely to signal the start of a major American intervention there. Instead, it would likely be in the service of a pair of abstract—but very important—principles.

The first principle is American credibility. It was almost one year ago that Obama declared the use or movement of chemical weapons in Syria a “red line” that would force him to rethink his “calculus” about that country’s conflict. When regime forces went ahead and launched chemical attacks anyway, the White House—after months of delay—announced in June that the U.S. would increase the “scale and scope” of its support for the Syrian rebels. But the move seemed halfhearted at best, reflecting Obama’s fear of being dragged into a messy sectarian conflict. Earlier this month the Los Angeles Timesreported that “U.S. weapons and ammunition have not reached America’s allies among the Syrian rebels, and their delivery date remains unclear.” It would be little surprise if Assad concluded that Obama’s red line was empty talk.

It’s dangerous for a President’s threats to seem empty. Foreign leaders listen carefully to pronouncements from Washington to determine what they can get away with. Bad things often don’t happen because the consequences are made clear to America’s rivals beforehand. This principle is especially important now, as Iran weighs whether Obama’s vow to use military force to prevent Tehran from developing a nuclear weapon is serious. The more likely Iran thinks Obama is to use force, the less likely he’ll need to do it. “When you do have a red line, you’ve got to do something about it,” says Dennis Ross, a former Obama national-security aide who handled Iran policy. Particularly after the world has seen images of dead children.

The second goal is about enforcing a taboo. Obama wants to send a clear message—not only to Assad but to the world—that the international community views chemical weapons with special contempt. Here’s how Obama explained it in May:

[T]he use of chemical weapons would be a game changer, not simply for the United States for but the international community. And the reason for that is that we have established international law and international norms that say when you use these kinds of weapons, you have the potential of killing massive numbers of people in the most inhumane way possible, and the proliferation risks are so significant that we don’t want that genie out of the bottle.

Skeptics may wonder why nerve gas is any more inhumane than explosives that blow off limbs and rip bodies open, or the organ-crushing thermobaric bombs used by the U.S. and Russia. Some even question whether chemical weapons really can kill on a “massive” enough scale to be considered weapons of mass destruction. But along with the instinctive revulsion toward poison is the fear that the more Assad mixes and transports his chemical arms, the more likely they are to fall into the hands of terrorists who might try to use them against Israel or Western targets. And it is true that a well-executed terrorist attack with nerve gas could be terrifyingly lethal.

Obama could serve his two goals with limited strikes on a handful of military targets, probably by means of cruise missiles that involve no risk to U.S. personnel. The goal would be to impose a cost on Assad that outweighs whatever he thinks he gained by gassing hundreds of people near Damascus last week, as he is accused of doing. In doing so, Obama could hope to deter Assad from using his chemical arsenal again. And to demonstrate to the rest of the world, and especially to Iran, that he means what he says. Anyone hoping for more will likely be disappointed.